Recently techniques for recording digital signals obtained by transforming audio signals, which are analogue signals, on a tape are being developed with the development of the digital audio techniques. Since an extremely wide frequency band exclusively used therefor is necessary for transforming analogue signals into digital signals, it is required that the contact area per unit time in a magnetic head for recording signals on a tape or reproducing them is large. For this purpose, since it is an indispensable condition to adopt a rotating head system instead of the conventional fixed head system, heretofore various kinds of tape recorders provided with a rotating head based on such a condition have been proposed.
In such a tape recorder tape loading, by which the tape is drawn out and wound round a rotating head, is effected after cassette loading. At this time the reels rotate in accompany with extraction of the tape. In this case, a certain tension should be applied to the reels. Unless otherwise, the tape is drawn out too much and therefore there is a fear that looseness, etc. is produced in the tape.
Heretofore there was known a band brake applying backtension to the supply reel at the play in order to prevent it. However its principal object is tape tension servo and not prevention of the looseness in the tape. Consequently a construction, by which a preload brake for tape loading and play is incorporated in the same mechanism, has been proposed and realized in practice.
However, in the case where a preload brake is used, there are a number of problems that at the play, in addition to the band brake, the load due to the preload brake is applied and thus it is necessary to increase the driving force of the reel, etc.